The pharma giant also announced new funding of over US$1bn from the US Biomedical Advanced Research and Development Authority for the project.
Expenses for the vaccine, which will not be produced for a profit during the pandemic, are expected to be offset by funding by governments.
“AstraZeneca recognises that the vaccine may not work but is committed to progressing the clinical program with speed and scaling up manufacturing at risk,” the firm commented.
The licence agreement with Oxford University, which is developing the candidate, has been finalised and the vaccine is now known as AZD1222.
The first deliveries will start in September to distribute jabs to the 30,000 participants of the final phase of clinical trials.
The second phase on over 1,000 healthy volunteers aged 18 to 55 years has been concluded and data is expected shortly.
The FTSE 100-listed firm has concluded the first agreements for at least 400mln doses, while it is in talks with parallel supply chains to ensure the delivery of a globally accessible vaccine.
The US ordered 300mln doses, the Department of Health and Human Services revealed on Thursday.
It is engaging with international organisations such as the Coalition for Epidemic Preparedness Innovations, Gavi the Vaccine Alliance and the World Health Organisation, as well as governments, to ensure fair allocation of the vaccine.
Shares dipped 1% to 8,754p on Thursday in early trades.